In Pursuit of Perfect TV Color, With L.E.D.’s and Lasers

Sunday

Jun 24, 2007 at 4:33 AM

Several manufacturers are replacing bulbs in televisions with lasers and light-emitting diodes, which beam red, green and blue light rather than white light.

ANNE EISENBERG

HIGH-DEFINITION television sets grow ever more sophisticated, but the colors on many of the screens are still created the old-time way: with tubes or bulbs that give off white light that is filtered into primary colors and remixed.

Now, several manufacturers are replacing these bulbs with lasers and light-emitting diodes, or L.E.D.’s. These lasers and L.E.D.’s do not beam white light, but rather its three basic building blocks: red, green and blue. Beams are emitted in a narrow band of wavelengths very close to those of single, pure colors, giving off the brilliant, saturated red of a blazing sunset or the shimmering, luminous blue of a rainbow.

Beam these three primary colors in varying intensities at the same spot on a television screen, and a palette of hues can be created in a wider range than in TVs without this technology.

The new lighting is already built into a handful of commercial TV sets. Last year, Samsung Electronics America, of Ridgefield Park, N.J., introduced its first TV with L.E.D.’s. This year, the company has added six more, all large-screen, high-definition models.

The L.E.D.’s within the sets, which are all rear-projection models, are made by Luminus Devices, of Woburn, Mass. They emit beams of red, green or blue light when current is passed through the semiconductor chips that house them. The L.E.D.’s are expected to last the lifetime of the TV, unlike the bulbs typically used in these rear-projection TVs, which must typically be replaced every few years at a cost of about $200 to $350.

Laser TVs, unlike L.E.D. models, are not yet on the commercial market, but several manufacturers have demonstrated them at trade shows. Frank DeMartin, vice president for marketing and product development at Mitsubishi Digital Electronics America in Irvine, Calif., said the company would show a large-screen laser TV at the Consumer Electronics Show in Las Vegas next January. “It will spawn a new category for the premium end of the market,” he said.

The distinctive range of colors produced by lasers and L.E.D.’s may provide a competitive edge for rear-projection TVs, which have steadily lost market share to plasma and liquid crystal display models, said Paul Semenza, vice president for display research at iSuppli, a market research firm based in El Segundo, Calif.

ISuppli expects that 5.3 million rear-projection sets will be sold worldwide this year, making them the smallest segment of the TV market. In contrast, 74 million L.C.D. sets and 11 million plasma sets are projected to be sold, Mr. Semenza said.

Large-screen rear-projection TVs traditionally cost less than L.C.D. or plasma models with similar sizes of screens, but the rear-projection TVs are as much as 10 inches deeper.

“Consumers like thin,” Mr. Semenza said. “But innovation in color could stave off the competition.”

Consumers may also appreciate the longevity of L.E.D.’s and lasers in rear-projection TVs, compared with the bulbs they are replacing. Rear-projection sets are typically lit by high-pressure white-light mercury lamps. “After a year or two, the lamp goes out,” Mr. Semenza said. “You spend $3,000 on the TV and then have to buy a light bulb for $300.”

L.E.D.’s and lasers offer a more efficient design. “With light bulbs, you have violent high-voltage arcs across the metal electrodes,” he said. “Eventually the bulb fails because metal from the electrodes is knocked off.”

For the first Samsung model with L.E.D.’s, viewers paid a premium of $1,200 above the price of a similar model with standard lighting, said Dan Schinasi, senior marketing manager for HDTV product planning at Samsung. “This year the premium dropped to $300,” he said, “and as the year goes on, we’re hopeful the premiums will shrink even more.”

The sets use Luminus PhlatLight-brand L.E.D.’s. The red, blue, and green beams illuminate a Texas Instruments digital light processing chip where the image is created. This is a more direct method than starting with a white light source and filtering it into primary colors for recombination, said Chris Chinnock, president of Insight Media, a market research firm in Norwalk, Conn.

“You start with pure spectral colors and mix them very efficiently,” he said.

Lasers promise an even wider range of colors than L.E.D.’s, Mr. Chinnock said. “The lasers produce extremely saturated colors — the red is very red.” In contrast, he said, the red in many displays has a lot of orange in it. Because of that limitation, it is harder to show the range of shades that the eye can see, for example, between red and orange.

LASER light may also help rear-projection sets become thinner. “You can create some different architectures in how the light is folded and managed inside the TV,” Mr. Chinnock said, “so that you could potentially get a rear-projection laser TV that’s 6 to 8 inches deep.”

One of the lasers widely demonstrated at trade shows is made by Novalux, based in Sunnyvale, Calif. “The lasers will be able to give more than 90 percent of the color range that our eyes can see,” said Jean-Michel Pelaprat, chief executive of Novalux. “That’s not available from plasma displays and L.C.D.’s, whose color gamut reaches only 40 percent and 35 percent, respectively.”

L.C.D. televisions, too, may soon be affected by the new light sources, Mr. Chinnock of Insight Media said. The next step may be to eliminate the cold cathode fluorescent lamps that illuminate the sets from the back.

“The idea is to replace these lamps with a laser or L.E.D. light source in the back, and get much better color saturation,” he said.

Mr. Schinasi of Samsung said the company was interested in lasers as a light source but was sticking with L.E.D.’s for now. “The L.E.D.’s are getting at least 30 percent brightness boosts every year,” he said. “If that continues, we might not need lasers even for the 67-inch and 72-inch screens.”

Mr. DeMartin of Mitsubishi said he was holding out for lasers. “The bottom line is that the L.E.D.’s can’t reproduce some of the truly deep greens and reds as well as the laser,” he said. “The laser can do this better.”

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